Surface mapping of magnetic hot stars. Theories versus observations

TL;DR

This review compares observational surface magnetic and chemical maps of early-type stars with theoretical models, highlighting successes of 3D MHD models and challenges in atomic diffusion theories.

Contribution

It critically assesses the reliability of spectropolarimetric inversion techniques and compares empirical results with theoretical predictions for magnetic and chemical surface structures.

Findings

3D MHD models match observed magnetic field geometries

Atomic diffusion models struggle to reproduce observed abundance patterns

Observational techniques are critically evaluated for reliability

Abstract

This review summarises results of recent magnetic and chemical abundance surface mapping studies of early-type stars. We discuss main trends uncovered by observational investigations and consider reliability of spectropolarimetric inversion techniques used to infer these results. A critical assessment of theoretical attempts to interpret empirical magnetic and chemical maps in the framework of, respectively, the fossil field and atomic diffusion theories is also presented. This confrontation of theory and observations demonstrates that 3D MHD models of fossil field relaxation are successful in matching the observed range of surface magnetic field geometries. At the same time, even the most recent time-dependent atomic diffusion calculations fail to reproduce diverse horizontal abundance distributions found in real magnetic hot stars.